The present invention relates to a post-processing apparatus for stapling sheets carried out from an image forming apparatus such as a copier or a printer or for folding the sheets at a predetermined fold position. More particularly, the present invention relates to improvements in apparatus configuration allowing the apparatus to efficiently post-process continuously carried-out sheets.
In general, post-processing apparatuses which staples sheets carried out from an image forming apparatus or which folds the sheets into a booklet are well known. Such a post-processing apparatus comprises a plurality of sheet collecting means in order to post-process the sheets. For example, a first sheet collecting means collects and staples the sheets into a bunch. A second sheet collecting means folds the collected sheets into a booklet.
For example, Patent Document 1 (Japanese Patent Laid-Open No. 2000-63031) discloses an apparatus that selectively conveys sheets from an image forming apparatus through a path branching off to upper first sheet collecting means and lower second sheet collecting means. According to Japanese Patent Laid-Open No. 2000-63031, two staple devices are arranged in the sheet path leading to the first and second sheet collecting means. The sheets are collected at the staple position. The first staple device performs out end surface stapling by stapling the sheets at an end thereof, and the second staple device performs saddle stitching by stapling the sheets at the center thereof. Thus, the staple position is provided on one of the branching paths to staple and carry the sheets out to a first tray and a second tray. Then, the second sheet collecting means, positioned below the first sheet collecting means, folds the stapled sheets into a booklet and then carries out the sheets for housing.
Likewise, Patent Document 2 (Japanese Patent Laid-Open No. 2000-169028) switches sheets carried out from the image forming apparatus, back from a carry-in path and collects the sheets in sheet collecting means. The sheets are then stapled at the end surface thereof by a staple device located on a tray and then accommodated in a housing stacker located behind the tray. On the other hand, the sheet bunch on the tray are stapled at the center thereof and then guided to the front of the tray. The sheet bunch is folded into a booklet on a folding path located in front of the tray and is collected in a housing stacker.
Both, Patent Document 1 and Patent Document 2, adopt the apparatus configuration in which sheets are set and collected on the path (or tray) with the staple device located thereon, stapled, and then carried out to the first and second tray. Furthermore, Patent Document 3 (Japanese Patent Laid-Open No. 2004-269158) proposes an apparatus configuration in which sheets from an image forming apparatus are guided to a first path and a second path which branch off from each other, and are set and stapled on each of the paths, with the sheets on one of the paths directly carried out to a sheet discharging stacker and the stapled sheets on the other path folded into a booklet and then carried out to the sheet discharging stacker.
Further, Patent Document 4 (Japanese Patent Laid-Open No. 8-295448) discloses a mechanism used in an apparatus configuration having a driver unit and a clinch unit which are separate from each other, to support the units so that the positions of the units are movable in a sheet width direction. In Japanese Patent Laid-Open No. 8-295448, FIG. 20 shows a guide shaft that supports the driver unit so that the position of the driver unit is movable in the sheet width direction and a lead screw that moves the position of the unit. Further, FIG. 23 shows a guide shaft that supports the clinch unit so that the position of the clinch unit is movable in the sheet width direction, and a traveling wire that moves the position of the unit. A drive motor is coupled to the lead screw and the traveling wire and controlled to control the position of each unit.
Further, Patent Document 5 (Japanese Patent Laid-Open No. 2002-214973), discloses an end stapler that is located on a first tray positioned above a sheet conveying path to staple sheets at an edge thereof. A saddle stitching stapler is located on a second tray positioned below the sheet conveying path to staple the sheets at the center thereof. The sheet bunch loaded on the first tray is stapled at the edge (trailing edge) and then discharged to a downstream stacker. The sheet bunch loaded on the second tray are stapled at the center thereof, folded together, and then discharged to the downstream stacker.
Further, Patent Document 6 (Japanese Patent Laid-Open No. 2003-266405) proposes a mechanism that varies a direction in which needle points are bent, depending on the thickness of a sheet bunch. Japanese Patent Laid-Open No. 2003-266405 proposes an anvil unit which has a plurality of folding grooves and the position of which is adjusted relative to a driver unit to vary the bending direction of the needle point. Japanese Patent Laid-Open No. 2003-266405 further proposes that for a bunch of a normal bunch thickness, U-shaped needle points be bent so as to face each other and that for a bunch of a smaller bunch thickness, the needle points be folded in the same direction.
Further, Patent Document 7 (Japanese Patent Laid-Open No. 2004-269249) proposes an apparatus configuration which guides sheets from an image forming apparatus to a first path and a second path which branch off from each other and on each of which the sheets are set and stapled, with the sheets on one of the paths directly carried out to a sheet discharging stacker and the stapled sheet bunch on the other path folded together and then carried out to the sheet discharging stacker.
Patent Document 8 (Japanese Patent Laid-Open No. 2007-214973) discloses a post-processing apparatus having first trays arranged above and below a sheet carry-in path and a second tray located below the first trays so that sheets from the sheet carry-in path are housed on the first trays and housed on the second tray via a switchback path. A saddle stitching stapler is located on the second tray to staple the collected sheets at the center thereof.
When both stapling mechanism and sheet folding mechanism are incorporated into an apparatus, which sets and staples sheets carried out from an image forming apparatus or the like, folds the sheets into a booklet, and executes post-processing such as punching on the booklet, as described above, the conventional apparatus configurations pose the following problems.
The consecutively carried-out sheets are not efficiently processed by the apparatus configuration in which the sheets are guided to the common path so that the sheet bunch collected on the path is stapled and carried out to the first and second stackers and in which the sheet folding mechanism is located in one of the paths to the stackers as in the case of Patent Document 1 (Japanese Patent Laid-Open No. 2000-63031) and Patent Document 2 (Japanese Patent Laid-Open No. 2000-169028). For example, during the operation time when the staple device executes a stapling process on the collected sheet bunch, the carrying-out operation of the succeeding sheet must be stopped. Also, when a preceding sheet bunch is stapled at the end surface thereof by the staple device and then carried out to the first stacker and the succeeding sheet is stapled at the center thereof by the staple device and then carried out to the second stacker via the folding mechanism, the succeeding sheet cannot be processed until the preceding sheet bunch has been completed. Furthermore, when a trouble such as a sheet jam occurs in the staple device or the like, the succeeding sheet may be jammed requiring the whole apparatus to be shut down.
On the other hand, the paths are bent in the apparatus configuration in which sheets from the image forming apparatus are sorted, at a carry-in port, into the first and second paths and in which the end stapling process and the sheet folding process are executed on the respective paths as in the case of Patent Document 3 (Japanese Patent Laid-Open No. 2004-269158). With this configuration, cardboards for color printing or the like are difficult to handle. With a compact configuration, the paths must be bent in order to distribute the sheets to the first and second paths via the carry-in port. It is difficult for such a bent apparatus configuration to smoothly convey color printed sheets or the like which are relatively thick and which have a small coefficient of friction. This disadvantageously results in the increased size of the apparatus, frequent sheet jams, or the like.
It is therefore necessary that the sheets from an image forming apparatus should be stably conveyed, which is performed by carrying the sheets into the apparatus through a linear carry-in path and a switchback path. Further, the above-described problems can be obviated by constructing a first switchback conveying path and a second switchback conveying path which are arranged away from the carry-in path and installing a staple mechanism and a sheet folding mechanism in the respective switchback conveying paths.
It is therefore an object of the present invention to provide a post-processing apparatus performing a stapling finish and a sheet folding finish on sheets carried out from an image forming apparatus, wherein the apparatus is small and compact and is capable of stably executing processing.
Another object of the present invention is to provide a post-processing apparatus that, when a stapling finish and a sheet folding finish is to be placed on consecutively carried-out sheets, allows the succeeding sheet to be carried into the apparatus during one of the post-processing operations so as to allow the other post-processing operation to be performed on the succeeding sheet thereby allowing the consecutive post-processing operations to be efficiently performed.
Further objects and advantages of the invention will become apparent from the following description of the invention.